>>300880
You won't beat the main story without doing any crazy grinding, the same way you're not going to beat a beat-em-up without beating 'em up, or a shooter without shooting. If you want isometric strategy without the grind, there's Fire Emblem, FFTactics, XCOM and lots of standalones (Phantom Brave, Joan of Arc, Wild Arms XF, Tactics Ogre etc), but Disgaea is grind at it's core.
Honestly, they're best played as handheld titles. Emulate them on something portable and just chew on them quick whenever you've got time / a break between other things (weird to think that concept's a relic of a bygone era these days). Binging will burn you out fast and hard once you start hitting walls, but chewing slowly (grind during the week, progress at the weekend) will keep the temperature just right.